A driver assistance system for a motor vehicle, which includes at least one sensor for measuring the distance of the vehicle from an object, and a control unit for controlling functional groups of the motor vehicle as a function of the measuring result of the sensor, is described in PCT International Published Patent Application No. WO 02/084329. The control unit may be switched between a parking assistance operating mode and a pre-crash operating mode as a function of the velocity of the vehicle. The switchover between a speed control operating mode and the pre-crash operating mode depends on the movement of an object relative to the motor vehicle, which is measured by a sensor.
A parking assistance device for motor vehicles is described in European Published Patent Application No. 0 305 907. The motor vehicle has a transmitter disposed on the vehicle exterior, which emits a transmission signal radiated in the direction of a parking slot, and an associated receiver receives the reflected signal. The transmission signal is restricted to a small radiation angle and emitted transversely to the longitudinal axis of the motor vehicle, so that the reflected signals in the region of the parking slot, acquired while driving past the parking slot, differ clearly from the reflected signal outside the parking slot. On the basis of this clear signal difference the length of the parking slot is determined in a comparison device, taking a distance signal into account.
PCT International Published Patent Application No. WO 03/087874 describes a method for operating a parking assistance system for a vehicle, which has at least one distance sensor, which at least sectionally records the lateral close range of the vehicle. The vehicle also has a distance sensor, and a control device determines the length or width of the parking slot from the values of the sensors recorded while driving past the parking slot. In the process, the length or width of the parking slot is corrected by a correction value, and the measurement is implemented with the aid of a distance sensor at different time intervals, depending on the speed of the vehicle while driving past the parking slot.